Wolverine Is almost certinly the time traveler.It could be similar to comic with him In Kitty role and Xavier In rachel role.The rest In future may be killed off.

They could have a Back to the future style ending with Wolverine returning to future to find things much better.No sentinles.Cyclops alive as well as others who were previously killed.
He's only one who has memory of future with Sentinles.